In a large heavy bottomed saute pan, heat 1 Tbsp of oil. Remove the meat from the marinade, shaking off any excess. Reserve the marinade.
Cut the ham in half if that will make cooking it any easier. Remember, it's going to be shredded anyway. Sear the meat on all sides. Yes, you can put meat into the slow cooker without searing it first, but I like the extra flavor you get from browning the meat. The goal here is to render off a little of the fat and get some of the flavor you would get from roasting in the oven that you don't get in a slow cooker.
Set the slow cooker on high and put the piece with the most fat on it fat side down into the cooker. Pour over half the reserved marinade, including the onions. Put the other piece on top and pour over the rest of the marinade. Put the lid on and don't worry about it for the rest of the day, that's the beauty of a slow cooker. Try to resist the temptation to lift the lid and pull off a piece "just to check it." Needless to say, I failed miserably at this.
I put mine in, on high at 8am and then turned it down to low at 11am. It was probably ready to serve mid-afternoon, but I kept it in there until 6pm with no problem.
When ready to serve, remove the meat and shred into small pieces or chunks with a fork. Spoon some of the sauce from the pot over the top. Serve with black beans and rice or tortillas. If you want to serve in tacos, have some shredded cabbage, fresh cilantro, and sliced green onions for garnish.
Because I don't always have time to cook every component of every meal from scratch, I sometimes I have my own version of "semi-homemade." With this meal I wanted to serve black beans but didn't have time to make them from dried beans. Below is my quick recipe for black beans which turned out to be one of the hits of the dinner party (besides the pork, of course).